Radio plays but distorted sound

What is your question?

2003 Infiniti G35 sedan. Speakers are not the problem. CD plays fine. AM/FM are distorted and volume is uneven. All radio lights tone controls and buttons are OK. OEM radio original in car. Would like to fix and maybe add fully integrated Sirius/XM radio. No GPS. Want to keep all original if possible but don't want to pay factory price for radio head.

What makes this problem better or worse?

Sometimes it plays fine for short periods. CD and tape play OK all the time. Problem is isolated to AM/FM.

How long has your 2003 INFINITI G35 had this problem?

Have had car for a year. Problem developed over the last 4-6 months. We had speakers checked. They are OK